1. Field
Embodiments of the present disclosure relate to a cleaning robot having improved traveling performance and a method of controlling the same.
2. Description of the Related Art
In general, a cleaning robot is an apparatus which sucks up foreign substances such as dust, from a floor surface to clean a region to be cleaned while autonomously traveling about the region to be cleaned without manipulation of a user.
A cleaning robot is provided with a pair of driving wheels for traveling at both lower sides of a main body and at least one caster to support the main body to allow the main body of the cleaning robot to move forward, move backward, or rotate in a region to be cleaned. In the region to be cleaned where the cleaning robot travels, obstacles such as a step (door threshold), an object having an inclined surface, a piece of furniture, and the like may be present.
A robot including a main body with a low height such as a cleaning robot may enter a narrow space of an obstacle (e.g., space under a bed or sofa) so that an upper portion of the cleaning robot is jammed (hereinafter, referred to as ‘jammed state’), or a bottom surface of the cleaning robot may be caught by a structure or groove formed on the floor or the cleaning robot may climb on an obstacle so that driving wheels of the cleaning robot are lifted up (hereinafter, referred to as ‘lifted state’). Thus, the cleaning robot is often brought into a traveling-impossible state (hereinafter, referred to as ‘stuck state’). Besides, the cleaning robot may get stuck in a soft object such as bedclothes or clothes to be washed so that the cleaning robot is caught by an object (hereinafter, referred to as ‘object-caught state’), thereby causing a stuck state.
In conventional cleaning robots, a sensor to sense such ‘jammed state’, ‘lifted state’, or ‘object-caught state’ is not installed or an idling wheel is protruded by applying a suspension using a spring only when one wheel contacts the floor in the ‘lifted state’.
However, since conventional cleaning robots rely on force of springs, sufficient contact force may not be obtained when a wheel is lifted and it is difficult to escape from an obstacle even after the wheel contacts the floor. Since a wheel perpendicularly protrudes, it is impossible to escape from a jammed state of a side portion. In addition, conventional cleaning robots cannot escape from a jammed state of an upper portion thereof since a function of reducing a total height (length from the floor to a top portion of the main body) is not provided thereto.
Robots now under investigation may determine a stuck state by estimating a current status of the robot in real time by utilizing high-precision position estimation, image information, and the like. However, these techniques are not suitable for relatively small and low cost robots such as cleaning robots in which height, weight, and manufacturing costs are limited. In addition, a method of sensing a stuck state by using a current sensor of a wheel drive unit conventionally used in cleaning robots is not suitable for dealing with the stuck state after understanding a current situation since it cannot be applied to various situations. Since a location recognition technique via simultaneous localization and mapping (SLAM) by using a ceiling camera operates only when there are sufficient feature points on the ceiling parallel to the floor, it is not reliable when the cleaning robot is slanted in a stuck state, the cleaning robot enters a space under the furniture, or the like.